Mehrdad Abedi MD is a HematologylOncology postdoctorate fellow and a candidate for a K08 grant under the mentorship of Dr. Peter J. Quesenberry. The applicant wishes to pursue an academic career with his research focus in the field of stem cell biology. Marrow derived cells have the capacity to regenerate many different cell types in their appropriate tissues or in vitro. Functional stem cell plasticity connected with different phases of cell cycle and the transdifferentation ability of these cells have not been well charaterized. With cytokine driven cell cycle transit, adhesion protein expression, engraftment and differentiation fluctuates reversibly and these fluctuations appear to be tied to specific phases of cell cycle. The hypothesis is that the transdifferentation plasticity of marrow will also fluctuate with phase of cell cycle and that the critical initial event in this process relates to homing into different tissues. Besides giving dramatic new insights into stem cell biology, this project offers unique potential for various clinical tissue restorative approaches. We plan to study different marrow fractions (whole marrow, lin-sca+, rhodamine low Hoescht low, GFP+ Hoescht low side population, and clonally replaced marrow) through all points in a cytokine induced cell cycle tansit. We will determine the homing ability, short and long-term fate of these cells that go to heart, skeletal muscle and liver in untreated or organ injured mice and their ability to transdifferentiate in the above tissues. Two murine transplant models that allow for cell tracking will be used; the BALB/c male to female model and the B6 GFP transgenic model. Donor cells will be identified using FISH for the Y-chromosome and fluorescence or Ab staining for GFP. Immediate homing will be done marking the cells with a cytoplasmic dye. Double labeling approaches on frozen or paraffin sections will be carried out to identify donor origin and cell type. Mice will also be repopulated with "marked" marrow fractions and then hematopoietic mobilization will be done with or without heart, skeletal muscle or liver injury and again look at short and long-term cell fate and transdifferentation. High-speed cell sorting, fluorescent microscopy imaging and large event FACS analysis will evaluate short term homing. This project will explore the functional plasticity of marrow to transdifferentate into nonhematopoietic tissues (heart, skeletal muscle and in liver).